NEW YORK — During a bustling mid-afternoon Monday, a line of people snaked through the USTA National Tennis Center. It started from an entrance into Louis Armstrong Stadium, around Arthur Ashe Stadium and into the open mall in front of its main gate.

The orderly mass stood there with hopes of seeing Novak Djokovic play in his fourth-round match. What was a sign of populist desire to see him play also could be taken as another display of irreverence toward the U.S. Open’s top seed.

Despite being the world’s No. 1 player, Djokovic’s presence here has hardly matched his status within the sport. While his rivals earn top billing, he is sparsely visible away from the court. A dominant season has earned him respect but not marketability. His relegation to Armstrong, less than half the size of Ashe, was just another sign.

Roger Federer and Rafael Nadal, each of whom Djokovic has defeated on the way to his two Grand Slam titles this year, have a Nike store solely devoted to sell T-shirts adorned with their personal logos, mottos and images. Not to mention the innumerable fans walking around with “Vamos Rafa” or “Roger That” stamped across their chests.

Right across is a Lacoste store with a banner photo of Andy Roddick above the doorway.

“This is not just a New York thing,” said Simon Chadwick, a professor of sports business strategy and marketing at Coventry University Business School, and director at the Center for the International Business of Sport. “Djokovic’s commercial appeal and presence has been notable and conspicuous by its absence for several years now.

“At the heart of this is really understanding what the Djokovic brand is. When one thinks of Nadal, the picture of a toned, brooding, sexy Spaniard comes to mind. When one thinks of Federer, the picture of a cool, consummate, professional comes to mind. ... But with Djokovic, the nature and characteristics of the guy are not entirely clear and have never been accentuated. He has a great sense of humor, but this has never been used for commercial purposes and may not sit well with tennis officinados anyway.”

With a playful humor, a quick smile and easy demeanor, Djokovic would seem to beam with marketing potential. Before he began dominating the ATP, he was renowned for his imitations of fellow players on tour. Now, he is more known for having lost just twice in 63 matches this year.

Still, he has acknowledged that victory may not be enough to create a perception on the level of his peers.

“As much as you’re successful and as much as you win, you get more attention from the media and from the people, and you get more respect, obviously, from your colleagues,” Djokovic said last week. “But I think it’s really important as well to carry yourself off the court in a good way. ... I’m aware of the responsibility that I have as a present No. 1 to, you know, represent the sport. So I need to do that in a best possible way. I’m trying.”

In 2009, before he had cemented his place at the top of the sport, Djokovic signed a sponsorship deal with the Italian company Sergio Tacchini, leaving Adidas. Unlike Nike, which has created separate clothing lines for Federer and Nadal, Djokovic’s image has been more subdued.

“The Sergio deal is an interesting one that can be interpreted in some ways,” Chadwick said. “Clearly ST is not a brand that has the same strength or kudos as Nike or Adidas. Hence, Djokovic’s absence of commercial appeal may account for his signing with one of the more modest international apparel brands. But the failure to capitalize upon his success by the management team may also account for the failure to get a big deal with a bigger brand.”

At his first press conference at the U.S. Open, Nadal fiddled with a hat placed in front of him imprinted with his logo. Federer is more covert, sporting a shirt with his trademark merged “R” and “F” sign. At the podium, Djokovic has no such personal brand presence.

Perhaps it is reflective of his visibility around Flushing Meadows as well.

“I think I have to talk with my sponsors about it,” Djokovic said with a smile. “But, look, you know, I care mostly about obviously the game, to win on the court, and everything else I leave to the people who are responsible for that.”